void Householder<T>::evalHHmatrixData(const NDArray<T>& x, NDArray<T>& tail, T& coeff, T& normX) { // input validation if(!x.isVector() && !x.isScalar()) throw "ops::helpers::Householder::evalHHmatrixData method: input array must be vector or scalar!"; if(!x.isScalar() && x.lengthOf() != tail.lengthOf() + 1) throw "ops::helpers::Householder::evalHHmatrixData method: input tail vector must have length less than unity compared to input x vector!"; normX = x.template reduceNumber<simdOps::Norm2<T>>(); const T min = DataTypeUtils::min<T>(); if(normX*normX - x(0)*x(0) <= min) { normX = x(0); coeff = (T)0.; tail = (T)0.; } else { if(x(0) >= (T)0.) normX = -normX; // choose opposite sign to lessen roundoff error T u0 = x(0) - normX; coeff = -u0 / normX; if(x.isRowVector()) tail.assign(x({{}, {1, -1}}) / u0); else tail.assign(x({{1, -1}, {}}) / u0); } }
void Householder<T>::evalHHmatrixDataI(const NDArray<T>& x, T& coeff, T& normX) { int rows = (int)x.lengthOf()-1; int num = 1; if(rows == 0) { rows = 1; num = 0; } NDArray<T> tail(rows, 1, x.ordering(), x.getWorkspace()); evalHHmatrixData(x, tail, coeff, normX); if(x.isRowVector()) { NDArray<T>* temp = x.subarray({{}, {num, x.sizeAt(1)}}); temp->assign(tail); delete temp; } else { NDArray<T>* temp = x.subarray({{num, x.sizeAt(0)}, {}}); temp->assign(tail); delete temp; } }